In a third generation X-ray CT apparatus, an X-ray tube is positioned opposite an X-ray detector that has several detection segments, each of which has a plurality of detection elements. A patient is located between the X-ray tube and the X-ray detector. The X-ray tube and the X-ray detector rotate around the patient, such as 360 degrees, and X-rays are radiated from the X-ray tube to the patient. X-rays penetrated though the patient are detected by the X-ray detector as projection data. A tomographic image is reconstructed by a reconstruction equipment based on the projection data. Thus, the X-ray CT apparatus generally obtains the tomographic image, however, not only tomographic image but also fluoroscopic image of interested part of the patient can be needed in a surgery. It may be possible to set both X-ray CT apparatus and X-ray TV apparatus in the same surgery room, but it is difficult to install these two large sized apparatuses because a space in the surgery room restricted.
Japanese Patent Disclosure (Kokai 7-231888, pp 3–4, FIG. 1) describes that a fluoroscopic image is obtained by a 2-dimensional X-ray detector located opposite an X-ray tube, and a tomographic image and a 3D image are obtained based on projection data obtained by the same X-ray detector. Thereby, since the fluoroscopic image and the tomographic image are obtained by a single apparatus, the surgery room can be effectively used. The CT apparatus described in Japanese Patent Disclosure (Kokai 7-231888, pp 3–4, FIG. 1) has two X-ray detectors that are arranged mutually in the position of 90 degrees in order to obtain fluoroscopic images from two directions, which makes it easy to lead a needle or a catheter in a percutaneous surgery.
Japanese Patent Disclosure (Kokai 11-146874, pp 4, FIG. 1) describes that an X-ray film cassette or an X-ray flat detector is arranged in the position corresponding to an X-ray detector of X-ray CT apparatus. However, with this CT apparatus, it is necessary to set the X-ray film cassette or the X-ray flat detector at a predetermined position when a fluoroscopy image is obtained. With this CT apparatus, a collimator is set such that X-rays shape a sector in obtaining the tomographic image, and X-rays shape a cone in obtaining the fluoroscopic image. However, with the X-ray CT apparatus described in Japanese Patent Disclosure (Kokai 7-231888, pp 3–4, FIG. 1), the fluoroscopic image is distorted because the X-ray detector is arc shaped. With the X-ray CT apparatus described in Japanese Patent Disclosure (Kokai 11-146874, pp 4, FIG. 1), when the fluoroscopic image is obtained, it is necessary to set the X-ray film cassette or the X-ray flat detector, which makes it difficult to perform real time imaging.